1. Field of the Invention
The present invention relates to a data generator and a data generating method which utilize a quadrature signal composed of an I signal and a Q signal, and a transmitter utilizing this data generator.
2. Related. Art of the Invention
FIG. 25 shows an example of a conventional transmitter (for example, see Japanese Patent Laid-Open No. 2002-325109. The entire disclosure of the document are incorporated herein by reference in its entirety.). In FIG. 25, two output terminals of a data generator 5001 output I data (I signal) and Q data (Q signal) which are orthogonal to each other. These data are inputted to a modulator 5002 for modulation. A signal outputted from the modulator 5002 is amplified by an amplifier 5006. The amplified signal is then radiated from an antenna 5007.
However, in the transmitter shown in FIG. 25, the envelope of the signal outputted from the antenna 5007 varies markedly. The amplifier 5006 must be linear in order to prevent such a signal from being degraded in the transmitter. Ensuring the linearity of the amplifier 5006 causes the amplifier 5006 to consume more power.
In view of these problems, it is an object of the present invention to provide a data generator and a data generating method which serve to implement an efficient transmitter, and a transmitter utilizing this data generator.
The 1st aspect of the present invention is a data generating method comprising:
receiving an input signal to generate, from said signal, a quadrature signal composed of an I signal and a Q signal;
converting an amplitude component of said quadrature signal into a signal of a resolution lower than a resolution of said amplitude component;
dividing said I signal by the amplitude component of said quadrature signal to obtain normalized I data, multiplying said normalized I data by said converted signal to obtain first data, and outputting the first data; and
dividing said Q signal by the amplitude component of said quadrature signal to obtain normalized Q data, multiplying said normalized Q data by said converted signal to obtain second data, and outputting the second data.
The 2nd aspect of the present invention is a data generator comprising:
raw data generating means of generating, from an inputted signal, an I signal and a Q signal which are orthogonal to each other as well as an amplitude component of a quadrature signal composed of said I signal and said Q signal;
converting means of converting said amplitude component into a signal of a resolution lower than a resolution of said amplitude component;
first multiplying means of multiplying normalized I data obtained by dividing said I signal by the amplitude component, by said converted signal to obtain first data, and outputting the first data; and
second multiplying means of multiplying normalized Q data obtained by dividing said Q signal by the amplitude component, by said converted signal to obtain second data, and outputting the second data.
The 3rd aspect of the present invention is the data generator according to the 2nd aspect, wherein said converting means is delta sigma modulating means.
The 4th aspect of the present invention is the data generator according to the 3rd aspect, wherein said raw data generating means outputs said I signal, said Q signal, and said amplitude component,
wherein first dividing means connected to an output of said raw data generating means which outputs said amplitude component is connected to an output of said raw data generating means which outputs said I signal, and said first dividing means outputs said normalized I data by dividing said I signal by said amplitude component,
wherein second dividing means connected to the output of said raw data generating means which outputs said amplitude component is connected to an output of said raw data generating means which outputs said Q signal, and said second dividing means outputs said normalized Q data by dividing said Q signal by said amplitude component,
wherein said delta sigma modulating means is connected to the output of said raw data generating means which outputs the amplitude component,
wherein said delta sigma modulating means outputs a signal obtained by delta-sigma-modulating said amplitude signal,
wherein first multiplying means connected to an output of said delta sigma modulating means is connected to an output of said first dividing means, and said first multiplying means multiplies said normalized I data by the signal obtained by delta-sigma-modulating said amplitude signal, to obtain first data, and outputs the first data, and
wherein second multiplying means connected to the output of said delta sigma modulating means is connected to an output of said second dividing means, and said second multiplying means multiplies said normalized Q data by the signal obtained by delta-sigma-modulating said amplitude signal, to obtain second data, and outputs the second data.
The 5th aspect of the present invention is the data generator according to the 2nd aspect, wherein said raw data generating means outputs the normalized I data obtained by dividing said I signal by the amplitude component of said quadrature signal, the normalized Q data obtained by dividing said Q signal by the amplitude component of said quadrature signal, and the amplitude component of said quadrature signal.
The 6th aspect of the present invention is the data generator according to the 5th aspect, wherein said converting means is delta sigma modulating means.
The 7th aspect of the data generator according to the 2nd or 5th aspect, further comprising a fourth D/A converter and a fifth D/A converter which subject the first data and second data, respectively, outputted by said data generator, to D/A conversion.
The 8th aspect of the present invention is the data generator according to the 6th aspect, further comprising:
a first D/A converter connected to the output of said raw data generating means which outputs the normalized I data, of converting said normalized I data into analog data;
a second D/A converter connected to the output of said raw data generating means which outputs the normalized Q data, of converting said normalized Q data into analog data;
upsampling means connected to the output of said raw data generating means of upsampling the amplitude component of said quadrature signal; and
a third D/A converter connected to the output of said delta sigma modulating means, of converting said delta-sigma-modulated signal, into analog signal, and
wherein said delta sigma modulating means delta-sigma-modulates said upsampled signal,
wherein said first multiplying means is connected to an output of said first D/A converter and an output of said third D/A converter to multiply said normalized I data converted into analog data by said delta-sigma-modulated signal converted into analog signal and then to output a result of the multiplication,
wherein said second multiplying means is connected to an output of said second D/A converter and an output of said third D/A converter to multiply said normalized Q data converted into analog data by said delta-sigma-modulated signal converted into analog signal and then to output a result of the multiplication, and
wherein said first D/A converter and said second D/A converter have a higher vertical resolution than said third D/A converter, and said third D/A converter operates at a higher speed than said first D/A converter and said second D/A converter.
The 9th aspect of the present invention is the data generator according to the 2nd aspect, further comprising first delay means of delaying said I signal and second delay means of delaying said Q signal.
The 10th aspect of the present invention is the data generator according to the 2nd aspect, further comprising third delay means of delaying said normalized I signal and fourth delay means of delaying-said normalized Q signal.
The 11th aspect of the present invention is the data generator according to the 3rd or 6th aspect, wherein a low pass filter having a cutoff frequency higher than the half of a clock frequency of said delta sigma modulating means is connected to each of the outputs of said first multiplying means and said second multiplying means, to filter said first data and said second data.
The 12th aspect of the present invention is the data generator according to the 3rd or 6th aspect, wherein said delta-sigma-modulated signal is composed of data sequence of real numbers with two values having the same magnitude and different signs.
The 13th aspect of the present invention is the data generator according to the 3rd or 6th aspect, wherein said delta-sigma-modulated signal is composed of two values including 0 and a real number other than 0.
The 14th aspect of the present invention is a data generator comprising:
raw data generating means of generating, from an inputted signal, an I signal and a Q signal which are orthogonal to each other as well as an amplitude component of a quadrature signal composed of said I signal and said Q signal, and outputting normalized I data obtained by dividing said I signal by the amplitude component of said quadrature signal, normalized Q data obtained by dividing said Q signal by the amplitude component of said quadrature signal, and a signal which is obtained by converting a signal obtained from the amplitude component of said quadrature signal and which has a lower resolution than said amplitude component;
angle modulating means of angle-modulating said normalized I data and said normalized Q data to output said angle-modulated signal; and
amplitude modulating means of amplitude-modulating the angle-modulated signal outputted from said angle modulating means, using a signal obtained by converting amplitude data outputted by said raw data generating means.
The 15th aspect of the present invention is a transmitter comprising:
a data generator according to the 2nd or 5th aspect; and
vector modulating means of vector-modulating first data and second data outputted by said data generator.
The 16th aspect of the present invention is the transmitter according to the 15th aspect, wherein amplifying means is connected to an output of said modulating means, of amplifying said modulated signal,
wherein band pass means is connected to an output of said amplifying means, of passing a particular band of said amplified signal, and
wherein an antenna is connected to an output of said band pass means, for transmitting said passed band of the signal.
The 17th aspect of the present invention is the transmitter according to the 16th aspect, wherein an isolator is provided between said amplifying means and said band pass means.
The 18th aspect of the present invention is a transmitter comprising:
a data generator according to the 2nd or 5th aspect;
first vector modulating means of vector-modulating said first data and said second data;
second vector modulating means of vector-modulating said I signal and said Q signal; and
amplifying means of amplifying said vector-modulated signal, and
wherein when the transmitted signal has an intensity larger than a predetermined amount, the signal vector-modulated by said first vector modulating means is inputted to said amplifying means for amplification, and when the transmitted signal has an intensity smaller than the predetermined amount, the signal vector-modulated by said second vector modulating means is inputted to said amplifying means for amplification.
The 19th aspect of the present invention is a transmitter comprising:
a data generator according to the 2nd or 5th aspect;
third vector modulating means of vector-modulating said first data and said second data or said I signal and said Q signal; and
amplifying means of amplifying the signal vector-modulated by said third vector modulating means, and
wherein when the transmitted signal has an intensity larger than a predetermined amount, said third vector modulating means modulates said first data and said second data, and when the transmitted signal has an intensity smaller than the predetermined amount, said third vector modulating means modulates said I signal and said Q signal.
The 20th aspect of the present invention is a transmitter comprising a data generator according to the 2nd or 5th aspect; and
modulating means of modulating first data and second data outputted from said data generator,
wherein amplifying means is connected to an output of said modulating means, of amplifying said modulated signal,
wherein band pass means is connected to an output of said amplifying means, of passing a particular band of said amplified signal, and
wherein an antenna is connected to an output of said band pass means, for transmitting said passed band of the signal.
The 21st aspect of the present invention is the transmitter according to the 20th aspect, wherein said converting means is delta sigma modulating means, a signal outputted from said delta sigma modulating means has multiple values, and a predistorted signal to compensate for non-linearity of said amplifying means is inputted to said amplifying means.
The 22nd aspect of the present invention is the transmitter according to the 20th aspect, wherein a signal outputted from said delta sigma modulating means has multiple values, said amplifying means is composed of a plurality of amplifiers connected in parallel, and at least one of said plurality of amplifiers is selected in accordance with an envelope of the signal outputted from said delta sigma modulating means.
The 23rd aspect of the present invention is the transmitter according to the 15th aspect, wherein a process ending with an output from said modulating means comprises a digital signal process.
The 24th aspect of the present invention is a transmitter comprising:
a data generator according to the 2nd or 5th aspect;
first vector modulating means connected to an output of said data generator, of vector-modulating first data and second data outputted from said data generator;
first amplifying means connected to an output of said first modulating means, of amplifying a signal outputted from said first modulating means;
quantization noise generating means connected to said data generator, of outputting first quantization noise data generated by subtracting said I signal from said first data and second quantization noise data generated by subtracting said Q signal from said second data;
fourth vector modulating means connected to an output of said quantization noise generating means, of vector-modulating said first quantization noise data and said second quantization noise data;
second amplifying means connected to an output of said fourth vector modulating means, of amplifying a signal outputted from said fourth vector modulating means; and
combining means connected to an output of said first amplifying means and to an output of said second amplifying means, of combining the signal outputted from said first amplifying means and the signal outputted from said second amplifying means in substantially same amplitude and opposite phases, to cancel a quantization noise component.
The 25th aspect of the present invention is the transmitter according to the 24th aspect, wherein a low pass filter is connected to an output of said quantization noise generating means.